> You may be referring to a limitation of a certain OS regarding a hostname; or some network's policy.
No. See http://www.ietf.org/rfc/rfc810.txt
"ASSUMPTIONS
1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
to 24 characters drawn from the alphabet (A-Z), digits (0-9), and the
minus sign (-) and period (.).
..."
This defined a policy that was imposed by "The NIC" of the time. I believe the policy was relaxed somewhat after the DNS protocol was specified which allowed domain names to be longer than the NIC's policy, and the resulting confusion necessitated the clarification in 2181.
Regards,
-drc